String copy idiom.

[Daniel J. Salomon]

> The VAX 4.2 BSD UNIX library routine 'strcpy' uses code equivalent
> to the less efficient sequence:  while (*s++ = *t++);
> Perhaps it should be changed.
> 

SORRY for this error.
The idiom "while (*s++ = *t++);" generates the fastest possible code
if s and t are declared to be registers, which they are in the
system version of strcpy.  But note that if s and t are not in
registers then the sequence:
    while (*s = *t) {s++; t++;}
is more efficient.